Tissue kallikrein gene polymorphisms induce no change in endothelium-dependent or independent vasodilation in hypertensive and normotensive subjects

BACKGROUND

Tissue kallikrein (TK) generates Lys-bradykinin, which is then converted to bradykinin and releases nitric oxide (NO) from endothelial cells via B2 receptors. TK gene inactivation in mice causes severe endothelial dysfunction, which is also a hallmark of human primary hypertension (PH). Healthy carriers of a loss-of-function Arg to His substitution at position 53 (R53H) of the TK gene exhibit paradoxical arterial eutrophic remodeling. We therefore investigated the impact of this and other TK gene single nucleotide polymorphisms (SNPs) on endothelium-dependent vasodilatation (EDV) and endothelium-independent vasodilatation (EIV) in PH patients and normotensive (NT) subjects.

METHODS

The TK gene SNPs were genotyped blind to the phenotype by sequencing. We compared EDV and EIV vasodilatation across TK genotypes in 131 uncomplicated PH patients and 51 healthy NT subjects. EDV and EIV were assessed as the forearm blood flow response to a graded infusion of acetylcholine and sodium nitroprusside, respectively. We also evaluated the impact of the SNPs on NO-mediated EDV and on reactive oxygen species (ROS)-induced NO breakdown with the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine or vitamin C, respectively.

RESULTS

Genotypes and allele frequencies were in Hardy-Weinberg equilibrium and similar in PH and NT. EDV was lower in PH patients than in NT subjects. No TK genotype affected either EDV or EIV per se, or via interaction with gender and age. NO inhibition and scavenging of ROS showed no TK genotype effect on EDV. Similar conclusions were obtained with haplotype analysis.

CONCLUSIONS

These results do not support the contention that TK gene SNPs have a major impact in determining NO-mediated responses to acetylcholine.

The T(-786)C endothelial nitric oxide synthase genotype predicts cardiovascular mortality in high-risk patients

OBJECTIVES

This study sought to investigate the impact of a common T(-786)C single-nucleotide polymorphism (SNP) in the promoter of the endothelial nitric oxide synthase (eNOS, NOS3) gene on cardiovascular (CV) death in a prospective cohort study.

BACKGROUND

The T(-786)C SNP eNOS gene implies a blunted endothelium-dependent vasodilation in hypertensive patients and was associated with multivessel coronary artery disease in cross-sectional studies, but it remained unsettled whether it carried prognostic information.

METHODS

In consecutive white patients of the GENICA (Genetic and Environmental Factors in Coronary Atherosclerosis) study, who underwent coronary angiography between 1999 and 2001, we determined the incidence of CV death at follow-up. The eNOS T(-786)C and the exon 7 G(894)T SNPs were determined by melting curve analysis of amplicons from allele-specific fluorescence resonance energy transfer probes. Plasma levels of nitrate/nitrite, nitrotyrosine, and myeloperoxidase were also measured. The Kaplan-Meier and Cox regression analyses were used to assess the impact of SNPs on event-free survival.

RESULTS

Complete follow-up data were obtained in 1,086 (98%) patients. After a median follow-up of 1,296 days (range 4 to 2,057 days), we observed 85 (8.2%) CV deaths. There was a significant impact of the T(-786)C eNOS genotype on CV death-free (p = 0.0102) survival, but no differences in CV death rates across G(894)T genotypes. The TT individuals, who showed a lower survival, exhibited higher plasma myeloperoxidase (p < 0.0001) and lower levels of nitrotyrosine (p < 0.0001) than CC patients.

CONCLUSIONS

The T(-786)C SNP in the promoter of eNOS bears independent prognostic information and is associated with changes in markers of oxidant stress in high-risk white patients referred for coronary angiography.

Focal canine tetanus: diagnostic value of electromyography

A four-year-old, male Italian hound was presented with severe spasticity of both thoracic limbs that worsened with external stimuli. The remainder of the neurological and general physical examination was normal. Complete blood cell count, chemistry profile, and serology for protozoal diseases were within normal limits. Survey radiography of the cervicothoracic spine and abdominal ultrasonography showed no abnormalities. Electromyography of the thoracic limbs demonstrated the presence of "doublets" and simultaneous activity in both agonist and antagonist muscles. These abnormalities may be explained by a defective glycinergic inhibition at the spinal cord level. Together with the history, progression of signs, and clinical findings, electromyography supported a presumptive diagnosis of focal tetanus. The dog received tetanus antitoxin and antibiotic treatment and gradually improved over four months.

Adiponectin receptor expression in the human adrenal cortex and aldosterone-producing adenomas

Adiponectin is an adipocyte-derived circulating peptide that plays an important role in adipose tissue metabolism, insulin sensitivity and cardiovascular disease. The adrenal gland, by secreting glucorticoid and mineralocorticoid hormones, intervenes in cardiovascular and glucose metabolism regulation and is surrounded by adipose tissue. Hence, we investigated the hypothesis that adiponectin receptor types 1 and 2 (adipo-R1 and adipo-R2) are expressed in the human adrenal gland and in adrenocortical zona glomerulosa cell-derived aldosterone-producing adenoma (APA) tissue. We used real-time reverse transcription-polymerase chain reaction to demonstrate the mRNA of adipo-R1 and adipo-R2 in 10 histologically normal human adrenal cortexes that were obtained from patients with renal cancer undergoing nephrectomy with ipsilateral adrenalectomy and in 10 APAs. Melting curve analysis and sequencing were used to confirm the specificity of the amplicons obtained. Results consistently showed the expression of specific mRNAs of adiponectin receptors in all histologically normal human adrenal cortexes and APAs. This novel finding suggests that adiponectin could play a regulatory role in adrenocortical function and growth in humans.

Hyperhomocysteinemia predicts total and cardiovascular mortality in high-risk women

OBJECTIVE

The impact of homocysteine on cardiovascular disease can be more detrimental in women than in men, but it is unknown whether this applies to high-risk women. We therefore investigated the association of hyperhomocysteinemia with coronary artery disease (CAD) and cardiovascular mortality in high-risk women referred for CAD, both in the total population and in the hypertensive and normotensive cohorts.

DESIGN

A prospective study cohort.

SETTING

A tertiary centre.

PATIENTS

INCLUSION CRITERIA

262 consecutive Caucasian postmenopausal women referred for coronary angiography.

EXCLUSION CRITERIA

acute myocardial infarction and vitamin supplementation.

MAIN OUTCOME MEASURE(S)

We assessed total plasma homocysteine (tHcy), folate levels, and the MTHFR677C-->T polymorphism. CAD was defined as a modified Duke Index score greater than 0; hyperhomocysteinemia as tHcy levels of 15 micromol/l or greater. The primary study outcome was cardiovascular mortality at follow-up.

RESULTS

Mild/moderate and severe hyperhomocysteinemia was found in 15.1 and 1.6% of women, respectively, without differences between CAD and non-CAD women. By the ATPIII criteria, 92.2% of the women were in the highest risk class and 55% had CAD; however, no association of tHcy with the CAD score was found. After a median follow-up of 3.6 years, 23 women (9.1%) had died, 15 (6%) of cardiovascular causes. Women with high tHcy levels showed the worst all-cause and cardiovascular death-free survival at Kaplan-Meier and Cox regression analysis. Moreover, in the hypertensive cohort only women with hyperhomocysteinemia showed increased cardiovascular mortality.

CONCLUSION

Hyperhomocysteinemia is common in high-risk women and adversely affects their prognosis, although it is unrelated to the CAD atherosclerotic burden.